Desert clothing is a set of clothes designed for use in desert. There are two instances of the item defined in the rules.
In Dark sun, desert clothing costs 10 gp, weighs 3 pounds, and gives a +1 item bonus to endurance checks to resist environmental hazards, and is technically vaguely worded to include any environmental hazard. [DSCS:123]
In Mordenkainen's Magnificent Emporium, desert clothing is part of the Traveler's kit, costs 5 gp, weighs 4 pounds, and gives a +2 bonus to endurance checks to resist heat or avoid effects of persistent dust or sun glare.[MME:125]